1. Field of the Invention
The invention relates to the use of developer mixtures including carrier particles and toner particles, and more particularly relates to the use of such developer in electrostatic printing or copying devices.
2. Description of the Prior Art
Developer mixtures which are comprised of ferromagnetic carrier particles and electrically non-conductive toner particles are known. Such developer can be used, for example, in electrostatic stencil screen printing apparatus as exemplified by U.S. Pat. No. 3,306,193, and is useful in xerographic apparatus such as exemplified by U.S. Pat. No. 3,094,049. In the printing or copying operations performed by the prior art devices, the developer of toner and carrier is presented to a work station wherein toner, which is the electrostatic analogue of ink, is expended by the printing or copying operation. The carrier is a granular component of the developer and it is not expended during the printing or copying operation. Either process of the prior art requires that the developer be a homogeneous mixture or carrier and toner. Since toner is expended during the printing or copying processes, an initial homogeneous mixture of developer is converted to a heterogeneous mixture which is no longer suitable for quality performance of the printing or coating operations.